Eye to eye with a big ugly shark: Bigeye thresher stranded

When Martin Stehlik came to Whangarei from the Czech Republic to stay with his uncle, he didn't expect to come face to face with an unusual creature from the deep.

But on Saturday Mr Stehlik was on Ruakaka Beach with his uncle George Plesky when he came across an unusual sight, a relatively rare, four-metre bigeye thresher shark.

Mr Plesky, who lives in Whangarei, said he and his nephew were amazed when they saw the shark, which was on the beach, about half a kilometre south of the Ruakaka lifeguard station, and at first wondered just what it was.

"It was just so strange and we'd never seen anything like it before, with its long tail and it's big, black eyes. It was very unusual. Martin thought it might be a shark that isn't seen here often. He's going to go away with some very good memories of his time here," Mr Plesky said.

Department of Conservation shark expert Clinton Duffy was excited to see photographs of the shark sent to him by the Northern Advocate, saying it was a bigeye thresher shark (Alopias superciliosus).

"They're quite common but rarely seen due to their offshore habits. The feed on small schooling fishes and squid. Very little is known of the species' biology in New Zealand. New Zealand game fishers hold most, if not all of the world records for this species," Mr Duffy said.

Martin Stehlik with the shark. Photo / Supplied

He and Tom Trnski, from Auckland Museum, were hoping to get up to Ruakaka yesterday to collect some measurements and samples from the carcass to help increase the knowledge about the species.

The bigeye thresher shark is found in tropical and warm temperate waters and like other thresher sharks, nearly half its total length consists of the elongated upper lobe of the tail fin. Its common name comes from its enormous eyes, which are placed in keyhole-shaped sockets that allow them to be rotated upward.

The large eyes are adapted for hunting in low light conditions. It is one of the few sharks that conduct a diel vertical migration, staying in deep water during the day and moving into surface waters at night to feed. The bigeye thresher shark is rarely encountered by divers underwater and poses no danger.